Patients typically experience moderate-to-severe pain following knee arthroplasty that is usually treated with a combination of oral and intravenous analgesics and enhanced by continuous peripheral nerve blocks. There are currently two locations to place a perineural catheter to provide analgesia following knee arthroplasty: a femoral nerve catheter and an adductor canal catheter. Both have been demonstrated to be effective following knee arthroplasty. However, it remains unknown if one location is superior to the other; or, more accurately, what the relative benefits are to each technique.

While femoral CPNB has many benefits, one of the challenges of using this technique is that there is a decrease in quadriceps muscle strength which can be a limiting factor for rehabilitation. In contrast, the adductor canal catheter affects only the vastus medialis. This block may lessen block-induced quadriceps weakness following knee arthroplasty compared with a femoral infusion.

The investigators hypothesize that compared with femoral perineural local anesthetic infusion, an adductor canal infusion is associated with a shorter time until four discharge criteria are met: (1) adequate analgesia; (2) independence from intravenous analgesics; (3) ability to ambulate 30 m; and (4) ability to stand, walk 3 m, and return to a sitting position without another's assistance.

Discharge readiness is defined as meeting the following 4 criteria: (1) adequate analgesia (defined as pain less than 4 on a NRS of 0-10); (2) independence from intravenous analgesics; (3) ability to ambulate 30 m and (4) ability to stand, walk 3 m, and return to a sitting position without another's assistance.

Secondary Outcome Measures:

Time to adequate analgesia [ Time Frame: evaluated until discharge (and at least 72 hours) ] [ Designated as safety issue: No ]

Adequate analgesia is defined as pain less than 4 on a NRS scale of 0-10.

The timed-up-and-go (TUG) test measures the ability and speed of standing from a sitting position, walking 3 meters and returning to the original seated position independent from the assistance of healthcare personnel.

The control group will receive a femoral nerve catheter and block under ultrasound guidance with the final position of catheter posterior to the femoral nerve and lateral to the femoral artery. Normal saline up to 10ml will be injected if necessary for hydro-dissection via the needle. The catheter will then be threaded 3-5cm past the needle tip and its location will be confirmed by a 30ml bolus of lidocaine 2% via the catheter under ultrasound visualization. The control group will receive a standardized general anesthetic with inhaled volatile anesthesia in nitrous oxide and oxygen or bupivacaine spinal anesthetic.

The experimental group will receive an adductor canal catheter and block under ultrasound guidance with the final position of catheter between the femoral artery and nerve. Normal saline up to 10ml will be injected if necessary for hydro-dissection via the needle. The catheter will then be threaded 3-5cm past the needle tip and its location will be confirmed by a 30ml bolus of lidocaine 2% via the catheter under ultrasound visualization. The control group will receive a standardized general anesthetic with inhaled volatile anesthesia in nitrous oxide and oxygen or bupivacaine spinal anesthetic.

Detailed Description:

Of importance: The primary investigation involves 80 evaluable subjects (with primary endpoint data) having tri-compartment knee arthroplasty. In addition, the investigators will enroll up to 70 subjects having uni-compartment knee arthroplasty as a pilot study in preparation for a subsequent larger, definitive trial. These two groups will not be analyzed together--they represent two distinct studies: one a definitive RCT for tri-compartment knee arthroplasty; and, one a pilot study for uni-compartment knee arthroplasty.

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Please refer to this study by its ClinicalTrials.gov identifier: NCT01759277